Edge detection readout signal and cross-talk in phase-change optical data storage

Abstract

Conventionally, readout signal is obtained by differential detection in magneto-optical storage or by direct integration of the reflected light in phase-change optical storage. Mark edges are usually determined by slicing the level detection signal at the standard level, suffering from intersymbol interference when reading densely recorded short marks. Edge detection is a direct optical detection for mark edges. The readout signal is the difference signal from a split detector. Theoretically, edge detection has advantages over conventional level detection, such as high contrast and ability to identify edges of densely spaced marks. These features need to be confirmed experimentally. In magneto-optical storage [1], edge-shift of short marks using edge detection was found to be lower than that using differential level detection [2]. But in other aspects, such as signal and noise levels, edge detection was inferior to differential level detection [2, 3]. In phase-change optical storage [4], theoretical analysis indicates that edge detection has a potential superiority over conventional detection (hereafter referred to as sum detection). Experimentally, edge detection noise level has been confirmed to be lower than sum detection, especially at low and high spatial frequencies. In this work we present results for edge detection readout signal, carrier-to-noise ratio (CNR), and cross-talk characteristics in the scheme of land-groove as well as comparison with sum detection for phase-change optical storage.